The nature of the materials employed in water distribution circuits has a decisive influence on the extent of scaling. The liberation of Cu2+ ions into the water inhibits the nucleation and growth of calcium carbonate crystals. Thus, compared to other metals and polymers, copper shows a much lower scaling tendency. Furthermore, the presence of copper ions in the water, at concentrations well below the maximum permissible limits, decreases the scaling potential of the water with respect to other materials situated downstream.

The present study shows that copper becomes coated in calcium carbonate much less readily than other materials. This prevents the proliferation of bacteria such as those responsible for legionnaire's disease, which is generally facilitated by scale deposits. The influence of copper ions on the scaling potential of water was therefore determined first of all, followed by a study on the scaling behaviour of polyethylene. Real scaling was then studied on tubes of various types, in waters with widely different scaling potentials.